SEMESTER 2021 - SUMMER
University of Warsaw
Detecting long-lived multi-charged particles in neutrino mass models with MoEDAL
Monopole and Exotics Detector at the LHC (MoEDAL) is a mostly passive detector located in the LHCb cavern, just outside LHCb detector. MoEDAL was designed to search for magnetic monopoles, but it also sensitive to long-lived charged particles. A certain class of neutrino mass models predicts long-lived particles whose electric charge is four or three times larger than that of protons. Such particles, if they are light enough, may be produced at the LHC and detected. We investigate the possibility of observing those long-lived multi-charged particles with the MoEDAL detector. To demonstrate the performance of MoEDAL on multi-charged long-lived particles, two concrete neutrino mass models are studied. In the first model, the new physics sector is non-coloured and contains long-lived particles with electric charges 2, 3 and 4. The second model has a coloured new physics sector, which possesses long-lived particles with electric charges 4/3, 7/3 and 10/3. We explore the parameter space of these models and identify the regions that can be probed with MoEDAL at the end of Run-3 and the High-Luminosity LHC.
Looking forward to new physics and neutrinos at the LHC and beyond
New physics has traditionally been expected in the high-pT region at high-energy collider experiments. If new particles are light and weakly-coupled, however, this focus may be misguided: light particles are typically highly concentrated within a few mrad of the beam line. This opens up a novel direction in the LHC searches focusing on sub-GeV new particles and neutrino physics, which will be initiated by the FASER experiment during Run 3. In the talk, we will discuss the prospects of these and other related efforts that can extend towards the High-Luminosity phase of the LHC or even future proposed colliders. The focus of the talk will be on presenting the fields in both the Standard Model (SM) of particle physics and beyond the SM that could benefit from this research agenda.
University of Helsinki
I will introduce the novel phenomenon of CP-violating inflation which arises in models with several scalar doublets. The inert (without vacuum expectation value) doublets have a non-minimal coupling to gravity and play the role of the inflaton. I allow for this coupling to be complex, thereby introducing CP-violation - a necessary source of the baryon asymmetry - in the Higgs–inflaton couplings. I discuss the inflationary dynamics of such a model and show how the CP-violation is imprinted on the particle asymmetries after inflation in the hot big bang universe.
University of Warsaw
Light feebly interacting massive particle: freeze-in production and galactic-scale structure formation
Feebly interacting massive particles (FIMPs), contrasting with weakly interacting massive particles (WIMPs), is an intriguing dark matter candidate. Light (keV-scale) FIMPs produced by the freeze-in mechanism is of particular interest in that the structure formation of the Universe with FIMPs differs from that with WIMPs on galactic scales. The galactic-scale structure formation has been probed in many independent ways: Lyman-alpha forest spectra and the number of satellite galaxies in the Milky Way. We discuss the current constraints from observed galactic-scale structure and future prospects. Particular stress is placed on that the details of the production processes can impact the obtained constraints.
Technische Universität München
Confronting lepton number violating interactions with experiments and cosmology
The possibility of new physics in terms of lepton number violating (LNV) interactions is intriguing out of various reasons: LNV could be tightly linked to the generation of neutrino masses of Majorana nature while having severe implications on the generation of the baryon asymmetry of our Universe. In my talk, I will discuss different possibilities to probe LNV interactions including rare meson decays, neutrinoless double beta decay, and the LHC. Motivated by the goal of the NA62 experiment to reach SM precision in K????, I will first investigate what a deviation from the SM expectation would imply for new physics and baryogenesis. In the second part, I will focus on the consequences of observing LNV at the LHC or neutrinoless double beta decay experiments. I will demonstrate the crucial complementarity of these experiments and discuss the implications on baryogenesis models.
The Flavor of UV Physics
New physics not far above the TeV scale should leave a pattern of virtual effects in observables at lower energies. What do these effects tell us about the structure of a UV theory? We will address this question by considering the Standard Model as an Effective Field Theory, which allows us to relate physics at different energy scales through the renormalization group. I will show how to deduce possible features of a UV theory by combining top-quark observables at the LHC with bottom observables at the flavor factories.
Freeze-in produced dark matter in the ultra-relativistic regime
When dark matter particles only feebly interact with plasma constituents in the early universe, they never reach thermal equilibrium. As opposed to the freeze-out mechanism, the energy density of a feebly interacting state builds up and increases over the thermal history. In this talk, we address the impact of the high-temperature regime on the dark matter production rate, where the dark and Standard Model particles are ultra-relativistic and nearly light-like. In this setting, multiple soft scatterings, as well as two-to-two processes, are found to give a large contribution to the production rate. Within the model we consider, namely a Majorana fermion dark matter accompanied by a heavier scalar, which shares interactions with the visible sector, the energy density can be dramatically underestimated when neglecting the high-temperature dynamics. We find that the overall effective high-temperature contributions give order one corrections to the Born production rate with in-vacuum masses and matrix elements.
Improved muon (g-2) Measurements and Supersymmetry
The electroweak (EW) sector of the Minimal Supersymmetric Standard Model (MSSM) can give rise to rich phenomenology at various collider and dark matter (DM) experiments. Interestingly, the EW sector of the MSSM can also account for the persistent 3 - 4 sigma discrepancy between the experimental result for the anomalous magnetic moment of the muon, and its Standard Model (SM) prediction. We use the direct search results from the LHC as well as indirect constraints from DM and muon (g-2) experiments to put both upper and lower bounds on the electroweak superpartner masses. As a next step, we assume that the upcoming result of the Run 1 of the “MUON G-2” collaboration at Fermilab yields a precision comparable to the existing experimental result with the same central value. We analyze the potential impact of the combination of the upcoming and the existing muon (g ? 2) data on the allowed MSSM parameter space. We find that in this case the upper limits on the superpartner masses are substantially reduced. In this way, a clear target could be set for future LHC EW searches, as well as for future high-energy electron positron colliders, such as the ILC or CLIC.